A magnetic resonance imaging apparatus is an imaging apparatus that excites a nuclear spin in an object placed in a static magnetic field with a radio frequency (RF) signal at a Larmor frequency and reconstruct an image from a magnetic resonance signal produced by the object in response to the excitation.
In the magnetic resonance imaging, there is a field of diagnosis that involves injecting a contrast medium into an object and imaging the process of absorption of the contrast medium into an affected part, such as a tumor, through the blood vascular system with the lapse of time, such as in an early phase and a later phase. The imaging of this type is referred to as dynamic imaging using a contrast medium. A gadolinium contrast medium or the like is used in a conventional dynamic imaging performed by a magnetic resonance imaging apparatus.
In the diagnostic imaging of liver or the like, in addition to the dynamic imaging using a contrast medium that is to be absorbed through the blood vascular system described above, an imaging method using a newly developed contrast medium (such as the contrast medium referred to as Primovist) that is absorbed by the liver cells themselves has become popular in recent years.
In the dynamic imaging described above, a series of imagings are performed at a plurality of times, such as before injection of the contrast medium and the early phase and the later phase after injection of the contrast medium. The series of imagings is referred to as a “series” herein. In one imaging series, imagings are performed under basically the same imaging conditions except that the imagings are performed at different points in time, such as before injection of the contrast medium, in the early phase and in the later phase. The imaging conditions include the part to be imaged, the number of imaging slices, the positions of the imaging slices, the resolution, and specifications including a parameter of a pulse sequence closely related to these imaging conditions.
In a dynamic imaging series, the imaging before injection of the contrast medium and the imaging in the early phase are successively performed each in about 1 minute. However, a certain length of time has to be waited until the contrast medium is absorbed in the affected part, such as a tumor, before starting the imaging in the later phase. Therefore, an idle time of 2 to 3 minutes or so occurs between the imaging in the early phase and the imaging in the later phase. During the idle time, the patient has to stay lying on the bed and wait for the subsequent imaging.
On the other hand, in testing of one patient using the contrast medium, another imaging series is often performed in succession in addition to the dynamic imaging described above. For example, an imaging series with higher resolution may be performed after the dynamic imaging series is performed.
In such a case, if the whole or part of the another imaging series that would otherwise be performed after the dynamic imaging series can be performed in the idle time of the dynamic imaging series, the total imaging time of the patient can be reduced, and the burden on the patient can be reduced.
However, the conventional magnetic resonance imaging apparatus performs time management and imaging condition management separately for each series and therefore cannot perform imaging by inserting an imaging series into another imaging series.
In diagnosis of a liver cell using a contrast medium, such as Primovist described above, a waiting time of about 20 minutes is required after injection of the contrast medium for Primovist to be absorbed in the liver cell. According to the conventional technique, the patient has to stay on the bed and wait for the 20 minutes to pass. The time of 20 minutes is long enough to change patients and complete the whole or part of the imaging of another patient, thereby reducing the burden on the patients staying and waiting on the bed and the total imaging time of the patients.
However, the conventional magnetic resonance imaging apparatus performs time management and imaging condition management separately for each patient and therefore cannot insert an imaging of another patient into the imaging of one patient to perform the imaging of the another patient before the whole of the imaging of the one patient is completed. If the imaging is performed by changing patients, the imaging technician has to manage the time after injection of the contrast medium for each patient with a stopwatch or the like on his own, for example.
In view of such circumstances, in order to enable efficient use of the idle time of the contrast medium imaging, there is a demand for a magnetic resonance imaging apparatus that can perform time management and imaging condition management for combining a plurality of series of imagings or imagings of a plurality of patients.